Nitrogen (N) addition typically increases nitrous oxide (N₂O) emissions, but the magnitude of this effect depends on land use type and intensity. Grazing has an important influence on grassland N dynamics, but it is not clear to what extent grazing may interact with N addition in affecting grassland N₂O emissions. We investigated the mechanisms underlying the individual and interactive effects of N addition and cattle grazing (control (CK), N addition (N), grazing (G), and N addition plus grazing (N + G) treatments) on N₂O emissions in a temperate meadow steppe by measuring N₂O fluxes, weather factors, vegetation parameters and soil properties from October 2017 to September 2018. The studied temperate meadow steppe was a source of N₂O emissions during the experimental period. Approximately 80 % of the annual N₂O emissions were released during the plant growing season. The highest N₂O emission was detected in the N + G plots, which indicated the grazing treatment amplified the stimulating effects of N addition on N₂O emissions. The results from structural equation model (SEM) suggested that N addition enhanced N₂O emission through increases in NH₄⁺-N concentration and soil potential net nitrification rate (N_nitri); grazing promoted N₂O emissions by increasing substrate availability directly via excreta or indirectly through trampling-associated soil aggregate disruption and substrate release. N₂O emissions increased most strongly with N addition and grazing due to the synergetic effects between animal trampling, animal excreta and available N on the processes of nitrification and denitrification. Overall, our results suggest that the interactive effects of grassland management and global change factors on N₂O emissions need to be considered for the accurate assessment of grassland greenhouse gas emissions.

添加氮 (N) 通常会增加一氧化二氮 (N ₂ O) 的排放，但这种影响的大小取决于土地利用类型和强度。放牧对草地氮素动态具有重要影响，但目前尚不清楚放牧与氮素添加在多大程度上相互作用对草地N ₂ O 排放的影响。我们研究了 N 添加和牛放牧（对照 (CK)、N 添加 (N)、放牧 (G) 和 N 添加加放牧 (N + G) 处理）对 N ₂ O 排放的个体和交互影响的机制通过测量 2017 年 10 月至 2018 年 9 月的 N ₂ O 通量、天气因素、植被参数和土壤性质，在温带草甸草原上进行了研究。所研究的温带草甸草原是 N 的来源₂实验期间的 O 排放。大约 80% 的 N ₂ O 年排放量是在植物生长季节释放的。在 N + G 地块中检测到最高的 N ₂ O 排放，这表明放牧处理放大了 N 添加对 N ₂ O 排放的刺激作用。结构方程模型（SEM）的结果表明，N添加通过增加NH ₄ ⁺ -N浓度和土壤潜在净硝化速率（N _{nitri ）来增加N 2} O排放；放牧促进 N ₂通过排泄物直接增加底物可用性或通过踩踏相关的土壤团聚体破坏和底物释放间接增加 O 排放。由于动物践踏、动物排泄物和有效氮对硝化和反硝化过程的协同作用，N _{2 O 排放量随着氮的添加和放牧的增加最为显着。}总体而言，我们的研究结果表明，为了准确评估草地温室气体排放，需要考虑草地管理和全球变化因素对 N _{2 O 排放的交互影响。}